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Lipid-Resistant Grades
Lipids are
fatty acid esters, a class of relatively water-insoluble
organic molecules , which are the “basic” components of
biological membranes. There are three forms of lipids :
phospholipids , steroids and triglycerides.
In the past
few years, the use of lipid or fat emulsions for IV
therapy has grown in popularity. The reason is that lipid
emulsions are better suited than are aqueous solutions for
administering certain drugs that may not be water soluble.
The medical
plastics industry required a lipid-resistant polycarbonate
which had improved chemical resistance to increasingly
aggressive IV solutions being developed.
At the same
time it had to bond well with conventional adhesives and
solvent-bonding techniques alongwith the features like
high strength , clarity , toughness and processability.
Although
polycarbonate has long been used safely and effectively
for IV connector components, fatty solutions can attack
the polymer while it is under stress load, causing
anything from minor crazing to cracks and leaks. Female
luer fittings are particularly susceptible to stress
cracking. Compounding the problem is that, as part of a
drive to reduce costs, IV sets may be left in place from
48 to 96 hours rather than changed out every 24 hours. The
longer the exposure, the greater the chance for
stress-related attack of the component. Polycarbonate can
be replaced with other expensive and often exotic resins,
but the cost can prohibit widespread use. In addition,
many bonding, joining, and other secondary operations must
be retooled to account for the different properties of the
new material.
Recently,
lipid-resistant poly-carbonate grades have been developed
for the IV component market. These products have many of
the attributes of standard polycarbonate grades but with
dramatically improved resistance to stress-related failure
when exposed to typical lipid emulsions.
Typical
applications for IVs include luer fittings, stopcocks,
“Y”-site medication ports, tubing connectors, spikes, and
other critical components that may be subjected to high
stress while in contact with these chemicals.
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